This invention relates to photographic materials having an improved antistatic property, and more particularly, it relates to silver halide photographic materials having an improved antistatic property and resistance to adhesion without exhibiting adverse influences on the photographic properties.
Since a photographic material is generally composed of a support having an electric insulating property and photographic layers, electrostatic charges are frequently accumulated by contact friction between or separation from the surfaces of the same or dissimilar materials during the production or use of the photographic material. The electrostatic charges thus accumulated cause various problems, but the most serious trouble is that accumulated static charge may discharge before development of the photographic material to cause lightening-like exposure of photosensitive emulsion layers, whereby in the development of the photographic film, spot-like, twig-like, or feather-like marks form. These marks are so-called static marks, and occurrence of the static marks greatly reduces the commercial value of the photographic film, or in some cases may result in complete loss of commercial value. For example, it will be easily understood that if such a static mark appears in medical or industrial X-ray films, etc., it may induce a very dangerous misdiagnosis. This phenomenon is a very troublesome problem since the occurrence of the phenomenon is first found only at the time of developing the photographic film. The static charges accumulated also cause secondary problems, such as dust attaching to the surface of the photographic film and preventing coating of coating compositions from being uniformly performed.
Static charges frequently accumulate during the production and use of photographic materials as noted above. For example, such charges may be produced by contact friction of a photographic film against rollers during the production of the photographic film, or by separation of the surface of the emulsion layer from the surface of the support during winding or rewinding of the photographic film. Static charges are also produced in a finished photographic film by separation of the emulsion layer surface from the base surface in the case of performing winding or rewinding of a photographic film or in X-ray films by contact, separation, etc., between the X-ray films and mechanical parts or fluorescent intensifying screens in an automatic camera for X-ray films. The occurrence of static marks of photographic materials induced by the accumulation of such static charges becomes more severe as the sensitivity of photographic materials increases and as the processing speed for photographic materials increases. In particular, since the sensitivity of photographic materials has become higher, and there is an increased likelihood that the photographic materials will be treated under severe conditions, such as high-speed coating, high-speed photographing, high-speed automatic processing, etc., static marks have become increasingly likely to form.
Also, if a static charge is accumulated on the surface of a subbing layer in the case of forming the subbing layer on a film support and coating thereon a hydrophilic colloid layer such as a photosensitive silver halide emulsion layer, uneven distribution of the static charge appears and results in uneven coating of the hydrophilic colloid layer, which is a serious defect.
In one of the methods of overcoming the problems caused by these static charges, the electric conductivity of the surface of a photographic material is increased to dissipate the static charge in a short period of time before the accumulated charge discharges in a film-damaging manner.
Therefore, various methods have hitherto been considered to improve the conductivity of the supports and various surface coating layers of photographic materials, and it has been attempted to utilize various hygroscopic materials and water-soluble inorganic salts as well as certain kinds of surface active agents, polymers, etc. For example, there are the polymers as described in U.S. Pat. Nos. 2,882,157, 2,972,535, 3,062,785, 3,262,807, 3,514,291, 3,615,531, 3,753,716, 3,938,999, etc.; surface active agents as described in U.S. Pat. Nos. 2,982,651, 3,428,456, 3,457,076, 3,454,625, 3,552,972, 3,655,387, etc.; and zinc oxide, semiconductors, colloid silica, etc., as described in U.S. Pat. Nos. 3,062,700, 3,245,833, 3,525,621, etc.
However, these many materials as noted above show specificities depending upon the kinds of film supports and photographic compositions. That is, they may give good results for a specific film support and specific photographic emulsions as well as specific photographic elements, but they are not only useless for the static prevention of other different film supports and photographic elements, but also exhibit adverse influences on the photographic properties thereof.
Particularly, static prevention for hydrophilic colloid layers is very difficult, and it frequently happens that the reduction in surface resistance is insufficient in low humidity conditions, and adhesion troubles occur in a photographic material itself or between a photographic material and other dissimilar matters at high temperature and high humidity conditions.
On the other hand, some materials have very excellent antistatic effects, but cannot be used for photographic materials since they exhibit adverse influences on the photographic properties of silver halide photographic emulsions, such as sensitivity, fog, granularity, sharpness, etc., or they form scum in a fix solution. For example, it is generally known that polyethylene oxide series compounds have a static prevention effect, but they frequently exhibit adverse influences on the photographic properties of silver halide emulsions, such as increasing fog, desensitization, reduction in granularity, etc.
In another method of overcoming the problems of photographic materials caused by static charges, the static potential of the photographic materials is controlled to reduce the generation of static electricity by friction and separation.
For such purpose, it has hitherto been attempted to use the fluorine-containing surface active agents described, for example, in British Pat. Nos. 1,330,356 and 1,524,631, U.S. Pat. Nos. 3,666,478 and 3,589,906, Japanese Patent Publication No. 26687/77 and Japanese Patent Application (OPI) Nos. 46733/74 and 32322/76 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), but it sometimes happens that the static preventing ability of the surface active agents decreases with the passage of time since they transfer or diffuse during the preservation of the photographic materials. Furthermore, when these fluorine-containing surface active agents are used with above-mentioned conductive materials, they sometimes reduce greatly the conductivity of the conductive materials.
Also for controlling the static potential of photographic materials, it has been attempted to overcome the aforesaid faults of the surface active agents by using fluorine-containing polymers as described, for example, in British Pat. No. 1,497,256, Japanese Patent Application (OPI) Nos. 15822/79 and 129520/77, Japanese Patent Publication No. 23828/74, British Patent Application No. 2,024,440 A, etc. However, when, for example, a copolymer of a polyethylene oxide-containing monomer and a fluorine-containing acrylic acid ester monomer is applied to photographic materials, it is attended by an increase in fog, desensitization, and reduction in granularity by the polyethylene oxide group, as described above. Also, when a copolymer of a quaternary nitrogen-containing monomer and a fluorine-containing acrylic acid ester is applied to photographic materials, it may be effective in the points of static prevention ability and the prevention of adhesion problems, but it exhibits serious adverse influences on the photographic properties of silver halide photographic emulsions, such as sensitivity, fog, etc. Thus, it is not very satisfactory to use these compounds for photographic materials.